You can delete your account details on Profile page: https://www.cellmapper.net/profile . On profile page click Delete Account and follow instructions.
Deleting your account will not delete your uploaded and contribute data, it will just delete all data that identifies you (username, password hash, email address). Your uploaded data will remain in an anonymized state. Once your account has been deleted, anyone will be able to register a user account with your old user name.
If you have CellMapper Premium Subscription, you can't delete your account. You have to cancel Premium subscription first via PayPal. If you do not have a PayPal account, please create a support ticket for us.